Position sensorless open loop control for motor drives with output filter and transformer

Abstract

A power converter, control apparatus and methods are presented for driving a permanent magnet motor or other load through a sine wave filter and a transformer, in which inverter output current is controlled using a current-frequency relationship to convert a desired frequency or speed value to a current setpoint, and the inverter output current is regulated to the current setpoint using a control algorithm with a bandwidth below the resonant frequency of the sine wave filter.

The following is claimed: 
     
       1. A power conversion system, comprising:
 an inverter operative to provide AC output power to drive a load; and 
 a controller operative to regulate at least one inverter output current according to a frequency or speed setpoint value via a control algorithm having a current-frequency relationship with a zero current value corresponding to a zero frequency value, and a bandwidth below a resonant frequency of a filter coupled between the inverter and the load. 
 
     
     
       2. The power conversion system of  claim 1 , wherein the controller comprises:
 a current-frequency control component providing a current setpoint value according to the frequency or speed setpoint value and the current-frequency relationship with the zero current value corresponding to the zero frequency value; and 
 a current control regulator component implementing the control algorithm to regulate the inverter output current according to the current setpoint value. 
 
     
     
       3. The power conversion system of  claim 2 , wherein the current control regulator component implements the control algorithm to regulate the inverter output currents according to the current setpoint value and at least one feedback signal or value representing the inverter output current. 
     
     
       4. The power conversion system of  claim 3 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       5. The power conversion system of  claim 2 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       6. The power conversion system of  claim 2 , wherein the controller includes a proportional-integral controller to regulate the inverter output currents, the proportional-integral controller having a bandwidth below the resonant frequency of the filter coupled between the inverter and the load. 
     
     
       7. The power conversion system of  claim 6 , wherein the controller regulates the inverter output current according to a current setpoint value derived from the frequency or speed setpoint value and according to at least one feedback signal or value representing the inverter output current. 
     
     
       8. The power conversion system of  claim 6 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       9. The power conversion system of  claim 2 , wherein the current control regulator component is a proportional-integral controller having a bandwidth below the resonant frequency of the filter coupled between the inverter and the load. 
     
     
       10. The power conversion system of  claim 9 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       11. The power conversion system of  claim 9 , wherein the current control regulator component implements the control algorithm to regulate the inverter output current according to the current setpoint value and at least one feedback signal or value representing the inverter output current. 
     
     
       12. The power conversion system of  claim 11 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       13. The power conversion system of  claim 1 , wherein the controller regulates the inverter output current according to a current setpoint value derived from the frequency or speed setpoint value and according to at least one feedback signal or value representing the inverter output currents. 
     
     
       14. The power conversion system of  claim 1 , wherein the controller comprises a rate limiter component limiting a rate of change of a received desired frequency or speed value to provide the frequency or speed setpoint value. 
     
     
       15. A method for controlling a power conversion system driving a load through a filter, the method comprising:
 determining a current setpoint value according to a frequency or speed setpoint value; 
 sampling at least one AC output current feedback signal or value of the power conversion system; and 
 regulating the at least one AC output current according to the current setpoint value and the at least one AC output current feedback signal or value using a control algorithm having a current-frequency relationship with a zero current value corresponding to a zero frequency value, and a bandwidth below a resonant frequency of the filter. 
 
     
     
       16. The method of  claim 15 , comprising limiting a rate of change of a desired frequency or speed value to determine the frequency or speed setpoint value. 
     
     
       17. The method of  claim 15 , wherein the current setpoint value is determined according to a current-frequency relationship with a zero current value corresponding to a zero frequency value. 
     
     
       18. The method of  claim 17 , wherein the current-frequency relationship includes a first portion with increasing current values corresponding to a first frequency range from the zero frequency value to a cutoff frequency value, and a second portion with a constant current value (I MAX ) corresponding to frequencies higher than the cutoff frequency value. 
     
     
       19. The method of  claim 15 , wherein the at least one AC output current is regulated using a proportional-integral control algorithm having a bandwidth below the resonant frequency of the filter. 
     
     
       20. A non-transitory computer readable medium with computer executable instructions for controlling a power conversion system driving a load through a filter, the computer readable medium comprising computer executable instructions for causing a processor when executed to:
 determine a current setpoint value according to a frequency or speed setpoint value; 
 sample at least one AC output current feedback signal or value of the power conversion system; and 
 regulate the at least one AC output current according to the current setpoint value and the at least one AC output current feedback signal or value using a control algorithm having a current-frequency relationship with a zero current value corresponding to a zero frequency value, and a bandwidth below a resonant frequency of the filter.